Generally, Red Hat Linux runs in run level 3 - full multiuser mode. The following runlevels are used in Red Hat Linux:
- 0
- Halt.
- 1
- Single user mode.
- 2
- Multiuser mode, without NFS.
- 3
- Full multiuser mode.
- 6
- Reboot.
If your machine gets into a state where it will not boot due to a bad /etc/inittab, or will not let you log in because you have a corrupted /etc/passwd or have simply forgotten your password, boot into single user mode by typing linux 1 at the LILO boot prompt. A very bare system will come up and you will be given a shell from which you can fix things.